Conventionally, regenerators and recuperators are employed to exchange heat between two fluid streams. Regenerators are employed to provide a cyclic heat interchange, alternatively receiving heat from hot gaseous products of combustion and transferring it to, and thus preheating, the combustion air. Typically, regenerators have a heat reclamation bed made of or filled with a packing material that stores and transfers heat. While large checkerwork (refractory) regenerators have been known for decades, a more recent development has been the introduction of integral burner-regenerators, also known as regenerative burners.
Rapid cycle regenerative burners have been adopted for air fired furnaces due to their high thermal efficiencies, simple design, and the small size required for heat exchange. In general, regenerative burners are provided in pairs, with one unit operating in a combustion mode and the other in an exhaust or flue mode. For twin units A and B, for example, unit B may be operated as a burner while hot flue gases are cooled by being passed through the bed of unit A which is operated as "flue". When the bed of unit A has reached the targeted temperature, the flue gases are redirected to the bed of unit B, now operating as flue, while unit A is switched to burner mode; heat stored in the bed of unit A is recovered as the combustion air at ambient temperature is passed through the hot bed and is preheated. Once the bed of unit B reaches the targeted temperature, unit B is again switched to burner mode while hot exhaust gases are redirected to unit A.
One disadvantage associated with regenerative burners is the fact that they are limited to relatively clean combustion processes since waste gases that contain particulates and other impurities tend to plug or foul the bed.
An example of a process generating exhaust gas containing significant amounts of impurities is glass melting where the flue gas may contain dust, typically picked up from glassmaking materials, volatile condensable matter, as well as corrosive gases. Although the thermal efficiency of directly fired glass melting furnaces can be improved by replacing the combustion air with oxygen or with oxygen-enriched air, the use of oxygen adds to the overall operation cost. Generally, oxy-fuel glass melting furnaces are operated without flue gas heat recovery through the regenerator beds.
Efficiency improvements and cost reductions continue to be needed, therefore, for oxygen fired glass melting furnaces and for other furnaces for which the hot flue gas produced in the furnace is not passed through the regenerator beds.
Accordingly, it is an object of the invention to provide a process that improves the efficiency and can reduce the consumption of oxygen and fuel in such furnaces.